Natural World Heritage Sites (NWHS), via their formal designation through the United Nations, are globally recognized as containing some of the Earth's most valuable natural assets. Understanding changes in their ecological condition is essential for their ongoing preservation. Here we use two newly available globally consistent data sets that assess changes in human pressure (Human Footprint) and forest loss (Global Forest Watch) over time across the global network of terrestrial NWHS. We show that human pressure has increased in 63% of NWHS since 1993 and across all continents except Europe.